Hereinafter, a multi-cell mobile communication system will be described in brief.
FIG. 1 is a diagram illustrating a basic concept of a cellular based mobile communication system.
Referring to FIG. 1, each base station (BS) can control a specific cell region allocated thereto. Each base station can provide a specific mobile communication service to a mobile station (MS) within a given zone. All base stations may provide a single mobile communication service or different mobile communication services.
A multi-cell based mobile communication system can be designed such that all base stations of a specific zone use a single frequency region. Accordingly, the multi-cell based mobile communication system may be affected by interference of several radio waves from neighboring cells. If interference generated from neighboring cells is not properly handled, system throughput may be affected by the interference.
For example, in FIG. 1, a specific mobile station (MS) can be located between cells of BS 1 and BS 2. Since the BS 1 and the BS 2 use a single frequency region, signals transmitted from the two base stations BS 1 and BS 2 similarly affect the mobile station in view of the location. Accordingly, if interference from other base station in the cell boundary is not considered when a communication system is configured, problems occur in that channel quality information (CQI) fed back from the mobile station to the base station is measured in exactly and system throughput cannot be optimized.
In a wireless access system, interference by other signals, unexpected noise, etc. may cause several problems. Generally, noise means an unwanted signal generated spontaneously, and interference means an unwanted signal generated artificially.
Examples of the unwanted noise include background noise, artificial noise, mutual modulation, and noise generated by a receiver. The unwanted noise may occur due to several reasons. Examples of a noise source generated spontaneously include atmospheric disturbance, background noise, and thermal noise generated in a receiver. If the unwanted noise can be reduced in the wireless access system, system throughput can be improved directly.
An example of the artificial noise source includes interference noise. The interference noise can be generated by signals of other communication system or electric system in a single band. Namely, a single frequency band may be affected by interference from other communication system or electric system intentionally or spontaneously.